Developing an Applicable Process in Treating Chlorophenol-Contaminated Soil Using Chemical And/Or Biological Means

受氯酚(CPs)污染土壤因具毒性，以生物降解處理時常受外界環境因子影響，導致處理失敗，後續處理成本增加。由文獻及本研究團隊之實驗數據顯示，可行生物復育之各種氯酚污染濃度約在100-200 mg/kg-soil 左右，但氯酚污染場址中除可行生物復育之低污染土外，亦常有稱為熱區(hot zone)之高污染土且其氯酚濃度可達50,000 mg/kg-soil。如何能確切、有效率的來處理此類高污染土壤? 我們研議開發一套化學和生物兩階段處理技術，此一技術將可滿足污染場址中所有高低氯酚污染土整治所需。此外，以模式預測全區整治所需時間，除可預估場址復育所需時間並可做為處理效益評估之依據，故亦為本申請案研究重點之一。生物復育技術中的生物自然降解是目前處理氯酚污染土壤最經濟也最易被接受的方式，但因氯酚毒性之故生物處理有其極限，當氯酚濃度過高時並不可行。此外，生物處理時間較長，對土地價值昂貴的台灣是否是最經濟選項，亦值得探討。目前有關高氯酚污染場址大多以包埋(capping)隔離，或將該土壤焚化處理，惟包埋法並無法有效去除土壤中氯酚，對周遭環境生態及健康影響風險大; 而燃燒高濃度氯酚土壤不符合物質永續利用且易產生戴奧辛。為兼顧處理時效及全區整治成功之必然，本研究提出以化學氧化處理接續生物復育或生物自然降解等階段來整治全區污染土壤並配合降解動力模式之運用估算全區整治所需時間。本研究室初步發現利用不同催化劑可在數小時內降解不同氯化程度之氯酚且降解程度達 80-100%，此一氧化技術不同於Fenton 法，不需調pH 且處理時土壤含水率低，故可在現地施作而不至有滲出水的問題。相關技術已獲國內2 項相關專利(2007 及2008)，此一新發現將可確保高氯酚污染土可處理性及本計畫之可行性。第一年成果顯示EDTA-Fe 及heme 分別處理低氯及高氯氯酚，也已求得最佳處理氯酚污染土量之催化劑與氧化劑劑量，並以大尺寸反應槽測試兩種催化劑處理氯酚污染土壤，而氯酚降解效果亦是目前已知最佳者，並已申請國內專利權中。相信本三年研究若能順利完成，將可提供氯酚污染場址中高/低污染場址一個有效率之處理技術及一套具時效性的全區整治策略，而此一處理策略亦將革新目前氯酚污染場址之處理方式，故特別再提出後續兩年計畫執行之申請。[[abstract]]Chlorophenol’toxicity decreases the successfulness of remedying a chlorophenol- (CPs-) contaminated site, yet increases the follow-up treatment costs because of the treatment failure. From the literature and the preliminary results in our group, we found that bioremediation worked for CPs-contaminated soil ranging from 100-200 mg/kg-soil. However the bioremediation method fails to treat the “hot zone”soil that contains chlorophenols as high as 50,000 mg/kg-soil. How can we be sure to treat soil with various amounts of chlorophenols at its optimal efficiency? In this proposal we are to develop a full remedial strategy for a CPs-contaminated site and a kinetic model to predict the time needed for remedying the site. Bioremediation followed by bioattenuation is the most economical and acceptable mean in treating CPs-contaminated soil, but the technique has its limits especial when the content of CPs is high. Besides, the bioremediation process usually takes time which may not be economically efficient due to the limited land space in Taiwan. For highly CPs-contaminated soil, capping and combustion are two possible alternatives to remedy, yet the former does not remove CPs and results in a greater risk on environment and human health; the latter does break CPs structure but produces even worse compounds, the dioxins. To remedy a full, not a part, of a CPs-contaminated site, we propose an oxidation followed by bioremediation or bioattenuation strategy to treat various CPs-contaminated-site soils. At the meantime models will be employed to fit the analyzed data and used as a tool to predict the time span of each remedial step. Moreover our group found that different catalysts degraded chlorophenol species differently. In hours CPs degradation reached 80-100%. This oxidation needs no soil pH adjustment and is conducted at minimal soil water content, which directly avoids the leachate problems.With this finding we are awarded with two Taiwan Patents in 2007 and 2008 and are confident that this project is doable and the highly CPs-contaminated soil can be treated rather efficiently. From our first year outcomes, the data showed that EDTA-Fe and heme are best catalysts found in treating chlorophenols. The optimal dosages of both catalysts and peroxide were also determined. Using the optimal dosage to treat CP-contaminated soil in a scale-up study, we were able to degrade the CPs in the greatest extent ever reported. We believe that upon the completion of this project a treatment strategy in treating a full CPs-contaminated site is to be developed, so are the most efficient treatment technologies. And the strategy will revolutionize the way we treat a CPs-contaminated site today.[[note]]NSC98-2221-E327-00